Abstract

The binding of transcription regulators to cis-regulatory sequences is a key step through which cells regulate expression of their genes. Due to gains and losses of cis-regulatory sequences and changes in the transcription regulators themselves, the binding connections between regulators and their target genes can change rapidly over evolutionary time, a process called transcription factor rewiring. The goal of this study is to determine, on a large scale, the rewiring of the transcription factors in Candida albicans, an opportunistic human pathogen, compared to Saccharomyces cerevisiae the non-pathogenic baker’s yeast. Previous work had created a library of activated zinc cluster transcription factors in C. albicans. In this work our target is to activate the remaining non-zinc-cluster transcription factors and predict their function through analysis of gene expression and cellular phenotypes. We used VP64, a strong trans-activation domain, for fusion to different DNA-binding domains for the activation of transcription factors, and bioinformatics tools to search for candidate rewired transcription factors in C. albicans. Transcription factors play key roles in cellular regulation and are critical in the control of drug resistance in the fungal pathogen C. albicans. We found that activation of the transcription factor Orf19.2752 (Adr1) conferred significant resistance against fluconazole. We found that Adr1 is involved in ergosterol biosynthesis in C. albicans. The rewiring from ergosterol synthesis to fatty acid metabolism involved all members of the Adr1 regulon except the alcohol dehydrogenase Adh2, which remains under Adr1 control in both circuits. The second part of our studies lead us to investigate a multi-branched sulphur metabolism pathway in detail. In the sulphur assimilation pathway, we have encountered multiple rewiring events whose functional details we are establishing.